<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>js 实现拖拽排序</title>
    <style>
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }
        
        .container {
            max-width: 450px;
            margin: 0 auto;
            padding: 15px;
        }
        
        h4 {
            padding-bottom: 15px;
        }
        
        ul {
            touch-action: none;
            user-select: none;
        }
        
        .column {
            margin-bottom: 15px;
        }
        
        .column-item {
            height: 50px;
            margin-bottom: -1px;
            padding-left: 15px;
            line-height: 48px;
            background: red;
            border: 1px solid #d6d6d6;
            list-style: none;
        }
        
        .column-item:first-child {
            border-radius: 5px 5px 0 0;
        }
        
        .column-item:last-child {
            border-radius: 0 0 5px 5px;
        }
        
        .grid {
            display: flex;
            flex-wrap: wrap;
            margin: 0 -15px -15px 0;
        }
        
        .grid-item {
            width: 90px;
            height: 90px;
            line-height: 88px;
            text-align: center;
            margin: 0 15px 15px 0;
            background: #FFF;
            border: 1px solid #d6d6d6;
            list-style: none;
        }
        
        .active {
            background: red;
        }
        
        .clone-column-item {
            position: fixed;
            left: 0;
            top: 0;
            z-index: 1;
            width: calc(100% - 30px);
            max-width: 420px;
            height: 50px;
            padding-left: 15px;
            line-height: 48px;
            background: #FFF;
            border: 1px solid #d6d6d6;
            opacity: 0.8;
            list-style: none;
        }
        
        .clone-grid-item {
            position: fixed;
            left: 0;
            top: 0;
            z-index: 1;
            width: 90px;
            height: 90px;
            line-height: 88px;
            text-align: center;
            background: #FFF;
            border: 1px solid #d6d6d6;
            opacity: 0.8;
            list-style: none;
        }
    </style>
</head>

<body>
    <div class="container">
        <h4>常规布局</h4>
        <ul class="column">
            <li class="column-item">item1</li>
            <li class="column-item">item2</li>
            <li class="column-item">item3</li>
            <li class="column-item">item4</li>
            <li class="column-item">item5</li>
            <li class="column-item">item6</li>
            <li class="column-item">item7</li>
            <li class="column-item">item8</li>
            <li class="column-item">item9</li>
            <li class="column-item">item10</li>
        </ul>
        <h4>Grid布局</h4>
        <ul class="grid">
            <li class="grid-item">item1</li>
            <li class="grid-item">item2</li>
            <li class="grid-item">item3</li>
            <li class="grid-item">item4</li>
            <li class="grid-item">item5</li>
            <li class="grid-item">item6</li>
            <li class="grid-item">item7</li>
            <li class="grid-item">item8</li>
            <li class="grid-item">item9</li>
            <li class="grid-item">item10</li>
        </ul>
    </div>
</body>

</html>

<script>
    class Draggable {
        constructor(options) {
            this.parent = options.element; // 父级元素
            this.cloneElementClassName = options.cloneElementClassName;
            this.isPointerdown = false;
            this.diff = {
                x: 0,
                y: 0
            };
            this.drag = {
                element: null,
                index: 0,
                lastIndex: 0
            }; // 拖拽元素
            this.drop = {
                element: null,
                index: 0,
                lastIndex: 0
            }; // 释放元素
            this.clone = {
                element: null,
                x: 0,
                y: 0
            };
            this.lastPointermove = {
                x: 0,
                y: 0
            };
            this.rectList = [];
            this.init();
        }
        init() {
                this.getRect();
                this.bindEventListener();
            }
            // 获取元素位置信息
        getRect() {
            this.rectList.length = 0;
            for (const item of this.parent.children) {
                this.rectList.push(item.getBoundingClientRect());
            }
        }
        handlePointerdown(e) {
            // 如果是鼠标点击，只响应左键
            if (e.pointerType === 'mouse' && e.button !== 0) {
                return;
            }
            if (e.target === this.parent) {
                return;
            }
            this.isPointerdown = true;
            this.parent.setPointerCapture(e.pointerId);
            this.lastPointermove.x = e.clientX;
            this.lastPointermove.y = e.clientY;
            this.drag.element = e.target;
            this.drag.element.classList.add('active');
            this.clone.element = this.drag.element.cloneNode(true);
            this.clone.element.className = this.cloneElementClassName;
            this.clone.element.style.transition = 'none';
            const i = [].indexOf.call(this.parent.children, this.drag.element);
            this.clone.x = this.rectList[i].left;
            this.clone.y = this.rectList[i].top;
            this.drag.index = i;
            this.drag.lastIndex = i;
            this.clone.element.style.transform = 'translate3d(' + this.clone.x + 'px, ' + this.clone.y + 'px, 0)';
            document.body.appendChild(this.clone.element);
        }
        handlePointermove(e) {
            if (this.isPointerdown) {
                this.diff.x = e.clientX - this.lastPointermove.x;
                this.diff.y = e.clientY - this.lastPointermove.y;
                this.lastPointermove.x = e.clientX;
                this.lastPointermove.y = e.clientY;
                this.clone.x += this.diff.x;
                this.clone.y += this.diff.y;
                this.clone.element.style.transform = 'translate3d(' + this.clone.x + 'px, ' + this.clone.y + 'px, 0)';
                for (let i = 0; i < this.rectList.length; i++) {
                    // 碰撞检测
                    if (e.clientX > this.rectList[i].left && e.clientX < this.rectList[i].right &&
                        e.clientY > this.rectList[i].top && e.clientY < this.rectList[i].bottom) {
                        this.drop.element = this.parent.children[i];
                        this.drop.lastIndex = i;
                        if (this.drag.element !== this.drop.element) {
                            if (this.drag.index < i) {
                                this.parent.insertBefore(this.drag.element, this.drop.element.nextElementSibling);
                                this.drop.index = i - 1;
                            } else {
                                this.parent.insertBefore(this.drag.element, this.drop.element);
                                this.drop.index = i + 1;
                            }
                            this.drag.index = i;
                            const dragRect = this.rectList[this.drag.index];
                            const lastDragRect = this.rectList[this.drag.lastIndex];
                            const dropRect = this.rectList[this.drop.index];
                            const lastDropRect = this.rectList[this.drop.lastIndex];
                            this.drag.lastIndex = i;
                            this.drag.element.style.transition = 'none';
                            this.drop.element.style.transition = 'none';
                            this.drag.element.style.transform = 'translate3d(' + (lastDragRect.left - dragRect.left) + 'px, ' + (lastDragRect.top - dragRect.top) + 'px, 0)';
                            this.drop.element.style.transform = 'translate3d(' + (lastDropRect.left - dropRect.left) + 'px, ' + (lastDropRect.top - dropRect.top) + 'px, 0)';
                            this.drag.element.offsetLeft; // 触发重绘
                            this.drag.element.style.transition = 'transform 250ms';
                            this.drop.element.style.transition = 'transform 250ms';
                            this.drag.element.style.transform = 'translate3d(0px, 0px, 0px)';
                            this.drop.element.style.transform = 'translate3d(0px, 0px, 0px)';
                        }
                        break;
                    }
                }
            }
        }
        handlePointerup(e) {
            if (this.isPointerdown) {
                this.isPointerdown = false;
                this.drag.element.classList.remove('active');
                this.clone.element.remove();
            }
        }
        handlePointercancel(e) {
            if (this.isPointerdown) {
                this.isPointerdown = false;
                this.drag.element.classList.remove('active');
                this.clone.element.remove();
            }
        }
        bindEventListener() {
            this.handlePointerdown = this.handlePointerdown.bind(this);
            this.handlePointermove = this.handlePointermove.bind(this);
            this.handlePointerup = this.handlePointerup.bind(this);
            this.handlePointercancel = this.handlePointercancel.bind(this);
            this.getRect = this.getRect.bind(this);
            this.parent.addEventListener('pointerdown', this.handlePointerdown);
            this.parent.addEventListener('pointermove', this.handlePointermove);
            this.parent.addEventListener('pointerup', this.handlePointerup);
            this.parent.addEventListener('pointercancel', this.handlePointercancel);
            window.addEventListener('scroll', this.getRect);
            window.addEventListener('resize', this.getRect);
            window.addEventListener('orientationchange', this.getRect);
        }
        unbindEventListener() {
            this.parent.removeEventListener('pointerdown', this.handlePointerdown);
            this.parent.removeEventListener('pointermove', this.handlePointermove);
            this.parent.removeEventListener('pointerup', this.handlePointerup);
            this.parent.removeEventListener('pointercancel', this.handlePointercancel);
            window.removeEventListener('scroll', this.getRect);
            window.removeEventListener('resize', this.getRect);
            window.removeEventListener('orientationchange', this.getRect);
        }
    }
    new Draggable({
        element: document.querySelector('.column'),
        cloneElementClassName: 'clone-column-item'
    });
    new Draggable({
        element: document.querySelector('.grid'),
        cloneElementClassName: 'clone-grid-item'
    });
</script>
